The present invention relates to secure chemical waste landfills and to methods of disposing of hazardous wastes in such landfills.
Hazardous chemical wastes are usually residues of chemical, manufacturing, or mining operations. Typical components of such wastes are heavy metals, e.g., chromium or lead and pseudo-metals, e.g., arsenic or selenium, persistent organic materials, frequently in the form of dusts, sludges or slimes.
The problem of the disposal of hazardous chemical waste has been exhaustively treated in the literature. Suffice to say, it is totally unacceptable to dump such wastes into conviently located excavations, or into streams or other bodies of water. Extraordinary care must be taken not to ecologically disturb the surrounding and underlying soil areas, or to pollute or contaminate natural resources. However, hazardous chemical wastes are a fact of life in our society and the safe and secure disposition of such wastes is of the utmost importance. Accordingly, it is a primary purpose of the present invention to provide a secure landfill and a method of utilizing such landfills which will minimize, and preferably eliminate entirely, contamination or ecological disturbance of the surroundings.
In recent years there has been a flurry of activity in the design of better and more secure landfills. The earlier designs secured the materials to be disposed of in the fill, but frequently failed to treat the leachate, some allowed the leachate to drain from the confines of the landfill to an outside location where it was subsequently treated, for example, U.S. Pat. Nos. 3,586,624; 3,705,851 and 3,859,798. Some proposed to recycle the leachate, e.g., U.S. Pat. No. 3,859,799. Some mixed the waste with soil and added the mixture to the landfill. More recently designs have been proposed in which the landfill has a sloping bottom leading to a leachate basin, e.g., U.S. Pat. No. 4,358,221. Landfills with divided areas, or vaults have been proposed, and separate leachate collection systems for each vault have been suggested, see U.S. Pat. Nos. 4,350,461 and 4,430,021.
It is highly desirable, and one of the attributes of the present invention, that the leachate from the landfill does not drain from the confines of the landfill, but rather drains to a single, common low point within the landfill area for collection. It is also highly desirable that the landfill have a minimum of leachate accumulation in the fill in order to reduce the resultant hydraulic gradients to the most practical minimum level. However, landfills typically occupy relatively large areas and the amount of atmospheric precipitation, rain and snow, which is collected in the present day leachate collection systems can increase the volume of the leachate which must be handled by more than four or five times the volume of the leachate generated using the present invention. Thus, until the fill is closed and sealed, the area of the fill acts as a large collection pond for atmospheric precipitation which is added to the leachate. The cost of handling and treating the cumulative leachate is significantly increased. Since it is not economically feasible to excavate, prepare and line and subsequently close and seal a single vault for each increment of waste, the problem of handling and treating leachate grows greater every time it rains.
In many jurisdictions it is not uncommon that the landfill operator is required to place money in a closure fund, typically in an amount that is sufficient to cover the expense of hiring an outside third party to close and secure the landfill. The closure fund is not fully released until the operator has closed and sealed the fill in a satisfactory and approved manner. Under such circumstances a landfill operator may have a substantial amount of money tied up in a closure fund for a period of several years.
The present invention seeks to provide an improved secure landfill, a method of operating such landfill, a solution to the excess leachate problem, and further, a means by which the landfill operator may incrementally close and seal off portions of the fill and thereby also incrementally reduce, or receive back, monies that the landfill operator originally deposited in a closure or escrow fund which is usually kept intact until the final permanent closing of the entire landfill.
Heretofore because of such economic considerations conventional landfill areas seldom ranged larger than from about three to about six to ten acres. In contrast the present invention enables a more efficient use of the landfill site and makes possible the economic operation of landfill areas on the order of from about twenty to as much as thirty to fourty acres. In this manner the present invention significantly lessens the total number of individual landfill sites that otherwise would be required.